The electronic computers in motor vehicles take the form in a known way of a microcontroller comprising, in addition to one or more microprocessors, electronic memories (flash, EEPROM [‘Electrically-Erasable Programmable Read-Only Memory’], RAM [‘Random Access Memory’], etc.), interface devices, etc.
Nonvolatile computer memories store computer programs, or ‘software’, consisting of a set of program code instructions to be executed by a microprocessor in order to perform the various tasks of said computer. Generally, three main types of software are stored in nonvolatile computer memories:                ‘Boot Software’, as it is known in English, to be executed particularly at the startup of the electronic computer for initializing same,        ‘Application Software’, as it is known in English, to be executed for performing specific tasks of the electronic computer,        reprogramming software, or ‘Loader Software’, as it is known in English, that can be used to modify all or part of the information (in particular the software and/or the calibration data) stored in nonvolatile rewritable memories of the electronic computer.        
Boot software and reprogramming software can also be the same software, then known as a ‘Boot Loader’.
These days, some electronic computers in motor vehicles are equipped with ‘flash memory’ type nonvolatile rewritable memories. In a known way a flash memory is generally organized into a plurality of segments on which operations can take place in parallel. Each segment is itself organized into a plurality of sectors, a sector corresponding to the smallest memory unit capable of being made the subject of an erasing operation. In addition, each segment is generally organized into a plurality of pages, a page corresponding to the smallest memory unit capable of being made the subject of a write operation.
For reprogramming a flash memory, in principle the contents of the sectors of the pages in which new information has to be written must be erased, then said new information written in the pages provided.
When the contents of a sector are erased, it is no longer possible to retrieve the information which was previously stored in this sector. It is therefore clear that erasing operations must be performed with caution, in order to ensure that the contents of one or more sectors are not erased by mistake.
FIG. 1 schematically represents the organization of a flash memory comprising two sectors Sa and Sb the physical memory addresses of which are interleaved.
Indeed, it can be seen that the two sectors Sa and Sb break down into a plurality of elements. The elements of said sectors Sa and Sb are arranged so that the flash memory comprises first of all the first element of sector Sa, then the first element of sector Sb, then the second element of sector Sa, then the second element of sector Sb, etc.
Conventionally, erasing requests indicate the physical memory address of the start of the memory area to be erased, as well as the size of the memory area to be erased starting from this physical memory address.
Clearly such an approach implemented for erasing the contents of sector Sa entails a risk of also erasing the contents of sector Sb, due to the fact that these sectors are interleaved.